The ABCs of Vitamin D

The ABCs of Vitamin D

Posted on Feb 1, 2011
By St. Luke's, Duluth MN

Vitamin D deficiency is most commonly associated with decreased bone density, which can increase the risk of osteoporosis and fractures. According to Dr. David Arvold of
St. Luke's Internal Medicine Associates, many studies have shown an association between low vitamin D levels and heart disease, hypertension (high blood pressure), diabetes, cancer, several autoimmune diseases, premenstrual syndrome, anxiety and depression. However, he cautions that while vitamin D supplements may decrease the risk of these conditions, there isn't enough proof at this time.

Our bodies naturally produce vitamin D when exposed to direct sunlight; however, factors like time of day, cloud cover, angle of the sun, smog and sunscreen can affect how much vitamin D we produce. Although most diets provide some amount of vitamin D, even vitamin D-fortified foods can't compensate for limited sun exposure and the impact of aging.

How much is enough?

The amount of vitamin D we need depends on factors like gender, age, skin color and pregnancy. According to the National Institutes of Health, infants and children should receive 400 international units (IU) of vitamin D per day, while older adults and people with limited sun exposure or darker skin tones require higher amounts. In addition, certain medications prescribed to reduce inflammation, lower cholesterol, support weight loss or control epileptic seizures can interfere with vitamin D metabolism, increasing the need for higher doses for patients taking these drugs.

"Many doctors believe that daily supplementation of 800 to 1,000 IU is desirable for all adults, a point of considerable discussion and debate," Dr. Arvold says. "In general, unless an individual has low levels of vitamin D or a condition that causes deficiency, intakes of more than 1,000 IU daily just aren't necessary."

This chart reflects the general daily recommendations for vitamin D intake:

Age

Male

Female

Pregnant

Nursing

0-12 months

400 IU

400 IU

1-13 years

600 IU

600 IU

14-18 years

600 IU

600 IU

600 IU

600 IU

19-50 years

600 IU

600 IU

600 IU

600 IU

51-70 years

600 IU

600 IU

71+ years

800 IU

800 IU

Sunshine, salmon and supplements

For younger adults, 10 to 15 minutes of summer sun three times a week without sunscreen usually produces enough vitamin D. At the same time, sun exposure also increases the risk of skin cancer, so it's important to apply sunscreen for longer periods. When it comes to food sources, most of the vitamin D in the American diet comes from fortified cereal, margarine, orange juice and milk, with fish being one of the few foods naturally high in vitamin D. But as the IU tally below indicates, most adults will need a supplement in order to get enough vitamin D: